Algivorous Cercozoa shape the community composition of cryptogamic covers, the dominant vegetation in Polar Regions

Soil algae are the most important primary producers where vascular plants are absent, as in the Arctic and Antarctica. They give rise to species-rich microbial food webs in biological soil crusts (biocrusts). The terrestrial snow- and ice-free areas are in permanent expansion as glaciers retreat, leaving behind extensive areas of uncovered rock and new soil. Biocrusts stabilize the soil surface and have an important role in soil development. However, the microbial food webs and the nutrient and energy flow to higher trophic levels remain largely unexplored. Here, we characterized the microbial predator-prey dynamics of polar soils by combining molecular and traditional culturing techniques. Using high-throughput sequencing of environmental samples, we assessed the biodiversity and function of soil protists, applying a trait-based approach for acquiring and describing functional traits, i.e., the feeding behavior of heterotrophic protists in relation to microalgae. The study encompasses the analysis of biocrust samples of three polar regions. In the Arctic, one region was sampled - Svalbard in the Arctic Ocean (78°N) in July 2021. In Antarctica, two regions were studied, i.e. King George Island (62°S) in the South Shetland archipelago of Maritime Antarctica and the Thala Hills oasis in Enderby Land, East Antarctica (67°S), between January and March 2022.在维管植物缺失的北极与南极地区，土壤藻类是最为关键的初级生产者。它们在生物土壤结皮（biocrusts）中孕育出物种丰富的微生物食物网。随着冰川消融，陆地无雪无冰区域持续扩张，遗留出大面积裸露岩石与新生土壤。生物土壤结皮可稳固土壤表层，并在土壤发育过程中发挥重要作用。然而，针对微生物食物网以及向更高营养级流动的养分与能量的相关研究仍存在大量空白。本研究结合分子生物学与传统培养技术，解析了极地土壤中的微生物捕食者-猎物动态关系。本研究通过环境样本高通量测序技术，结合基于功能性状的研究方法获取并描述功能性状——即异养原生生物与微藻相关的摄食行为——以此评估土壤原生生物的生物多样性与功能。本研究涵盖了三个极地区域的生物土壤结皮样本分析。北极区域共选取一处采样点：2021年7月于北冰洋斯瓦尔巴群岛（北纬78°）开展采样。南极区域共选取两处研究区域：分别为海洋性南极洲南设得兰群岛的乔治王岛（南纬62°），以及东南极恩德比地的塔拉山绿洲（南纬67°），采样时间为2022年1月至3月。